In general, for drying a wet washed drying object automatically, a related art dryer has the following system.
FIG. 1 illustrates a longitudinal section of a related art dryer schematically, and FIG. 2 illustrates a section across a line I-I in FIG. 1.
The related art dryer is provided with a body 100 having an introduction opening 101 in a front, a drying drum 30 rotatably mounted in the body 100 having a plurality of agitating pieces 30a projected from an inside circumference, a door 105 for selective opening/closing of the introduction opening 101, a motor 50 fixedly secured to the inside of the body 100 for generating rotating force, a belt 60 for transmitting the rotating force from the motor 50 to the drying drum 30, hot air guiding flow passages 10a, and 10b for guiding an air flow so that external air is introduced into the drying drum 30 and discharged to an outside of the body 100, and an exhaust fan 40 for generating forced air blow force so that the external air is introduced through the hot air guiding flow passage 10a and discharging to the outside of the body 100.
The dryer also provided with a microcomputer (not shown) for controlling operation of the dryer, a humidity sensing unit 110 for sensing humidity of an inside of the dryer during progressing drying, and a temperature sensing unit 111 for sensing a temperature of the inside during drying.
The drying operation of the related art dryer will be described with reference to FIG. 3.
FIG. 3 illustrates a flow chart showing the steps of a related art drying method.
Referring to FIG. 3, upon starting drying after introduction of the drying object into the drying drum 30 (S10), a drying time period is set and, then, the heater 20 and the motor 50 are put into operation.
In setting a drying time period in the related art drying method, humidity and so on are measured at regular intervals at the sensing unit, and, if n data are measured only an initially measured data and a finally measured data are compared, to progress the next course.
In the meantime, as the exhaust fan 40 is put into operation, the external air introduced into the body 100 through an inlet side of the hot air guiding flow passage 10a is heated to a high temperature to hot air as the external air passes through the heater 20, and forcedly introduced into the drying drum 30 through the hot air guiding flow passage 10a. Then, the hot air introduced into the drying drum 30 repeats circulation in which the hot air is discharged to an outside of the body 100 through an outlet side of the hot air guiding flow passage 10b while vaporizing moisture from the wet drying object owing to suction force of the exhaust fan 40.
Through above process, the drying drum 30 rotates in regular/reverse directions at regular intervals owing to a driving power transmitted thereto from the motor 50 through the belt 60, to lift and drop the drying object held therein with the agitating pieces 30a, during which the drying object is dried (S20).
Finally, if the set time period is passed (S30), operation of the heater 20 and the motor 50 is stopped to finish the drying (S40).
Though not shown, after finishing the drying, cooling is started for dropping an inside temperature of the dryer, and by finishing the cooling after performing the cooling for a preset time period, the door 105 can be opened. In this instance, a cooling time period is fixed in a range of about 5 minutes.
Therefore, if the drying is finished after drying is performed for the preset time period, after performing the cooling for a predetermined time period, the door 105 of the related art dryer can be opened.
However, the related art dryer and the method for controlling a dryer have the following problems.
First, because the next course is progressed with reference to comparison of the initially measured data and the finally measured data only, there is high possibility of wrong progression of the next course due to an error of the data, and an accurate measurement of moisture in a small drying object (approx. below 2 pounds) has been difficult since the moisture contained therein will be small, too.
Second, since the drying is required to be made within an initially set time period, the drying can not be completed if the drying is slow do to a large amount of the drying object, or the drying can be excessive if the drying object is small or the drying is fast.
Third, measurements of the amount of drying object and the water content have been difficult if the amount of the drying object is small.